Share DB setup data between multiple unit test classes

I'm not sure if true unit tests should strictly interact with external systems like databases, but mine do - the idea being my setup code ensures the DB is in a certain state, then my unit tests expect certain results from methods that get called; I need to check the DB-access code is doing the right thing.

I want to use the same DB test data in multiple test classes and not copy-paste it into each class' [TestInitialize] and I'm wondering how best to do this. Options seem to include:

1. Throw it all in an external .sql script and run this
2. Some sort of helper class with a static method

I would prefer the code to update the DB is part of my C# code but wondered if there is a more typical way MSTest projects might handle this?